Our recent trip to San Francisco wasn't really similar to the trip you'll be taking, as we only rented a car one day, to drive to Napa for the day. However, we were very happy with the deal we got from Avis, and they were very pleasant to deal with. The office was a short walk from Union Square, where we stayed at the Hotel Chancellor, located at 433 Powell St. The streetcar goes right by it :-) It was very reasonably priced. I believe the rate we paid was $153.00. It wasn't at all fancy, not huge by any means, but very clean and comfortable. We would definitely stay there again!

Best, Sandy in Illinois, USA